When a personal computer is powered on, a Basic Input/Output System (BIOS) is the first code executed. Conventional BIOS identify, test, and initialize system devices, such as hard disks and other hardware. In so doing, the BIOS prepares the personal computer so that operating system software can be loaded, executed, and given control. This process of preparing a personal computer is called booting up. Booting up a personal computer is often slow, especially when the computer's operating system is large, which is more and more often the case.
Not only can booting up a computer be quite slow, a user then waits for applications to load. If the user wants to check email or prepare a word-processing document, the user conventionally turns on the personal computer, waits for it to boot up, and then waits for applications to load.